Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
The electrolytic recovery of metal and in particular copper has been known for a considerable period of time. The first patents for metal electrorefining, were for copper and were granted to James Elkington in England in 1865. The first copper refinery was built in Newark by Balbach Smelting and Refining Company in 1883. Early electrorefineries had difficulty producing firm cathode deposits of high purity copper. The use of additives to the electrolyte, in particular salt and improved electrolyte circulation were the most important developments in overcoming the early difficulties. As the art of electrorefining grew so did the competition and it was secrets like this which were jealously guarded to retain an edge over a competitor. Even though electrolytic copper was being produced with higher purity and conductivity than fire refined Lake copper, it took many years before consumers gave recognition to this fact. Electrolytic copper became the official basis for price quotation in 1914.
During the early part of this century the industry grew rapidly with copper refineries being built throughout America, Europe and Australia. Large scale electrowinning of copper was developed between 1912-1915 at Chuquicamata Chile. As the industry grew to meet the consumer demands there were steady improvements in productivity mainly through mechanisation of the electrode handling.
The most significant change to the fundamental process of electrorefining of copper came with the development of the permanent stainless steel cathode technology, by I. J. Perry and others at the Copper Refineries Pty Ltd in Townsville, Australia in 1978.
Within a few years of its development, the permanent stainless steel cathode technology now known as the “ISA PROCESS” gained world wide acceptance and is recognised today as the bench mark for copper refining practices.
The fundamental difference between the ISA PROCESS and conventional starting sheet technologies is that the ISA PROCESS uses a permanent reusable cathode plate instead of a non-reusable copper starter sheet. The ISA PROCESS cathode plate is made of 316 stainless steel blade, approximately 3.25 mm thick which is welded to a hanger bar. In most cases the hanger bar is made of hollow stainless steel section and, to improve electrical conductivity, is encapsulated with a copper coating of the order of 3 mm thick.
The vertical edges of the cathode plate are masked with plastic strips to prevent the copper cathode growing around the edges. The bottom edge may also include a plastic edge strip, or be masked with a thin film of wax to prevent the copper enveloping the plate. After time appropriate in the electrolytic bath for deposition of copper, the cathode plate is stripped to produce two single sheets of pure cathode copper, from each side.
In some instances a V-groove may be formed in the bottom edge of the cathode blade. The resulting enveloped cathode has a flow or fracture line along the lower edge which allows the resulting enveloped cathode to be split into two pieces.
There have been a number of developments in methods and process equipment for electrorefining of metal. Much development work has concentrated on the structure and components that go to make up the cathode plate including the hanger bar, edge strips, cathode blade etc.
While the cathode plates of the ISA PROCESS are reusable, after some considerable period of use they may require repair or refurbishment. Such repair or refurbishment can be difficult particularly with certain types of cathode plates. For instance with cathode plates which have solid copper hanger bars, if the hanger bar is damaged it may be necessary for it to be removed and a new copper hanger bar to be welded to the plate.
When using a stainless steel hanger bar, with a copper cladding to improve electrical conductivity, the copper cladding may be damaged or require refurbishment. Such an operation can be difficult since it is vital that the copper cladding have a consistent thickness over the hanger bar and upper end portion of the cathode blade to ensure even and consistent electrical flow and to ensure the cathode plate sits in the correct vertical alignment in the electrolytic bath.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.